Back pain with leg pain caused by disc herniation is a complex problem and not one that is easy to diagnose. Physicians rely on the patient’s history, physical examination (including specific neurological tests) and imaging studies such as X-rays, MRIs and CT scans. Accurately identifying the problem is one step. Determining the spinal level where the disc is pressing on the spinal nerve is a separate diagnostic step.

It would be helpful for examiners evaluating patients with back and leg pain if they knew which clinical tests were the most accurate and reliable. This is especially true if it turned out that one neurological testing procedure could provide good overall diagnostic accuracy.

According to this study from New Zealand, current motor, sensory, and reflex testing used to diagnose disc herniation and specific level of pathology are not accurate. In fact, after pooling all the data together and analysing the studies published so far, it looks like the accuracy value of the tests is poor at best.

After searching six of the most relevant electronic databases, they found 14 studies that matched their inclusion criteria. Their search history, search strategy and algorithm for the studies was presented as an easily readable diagram. Study characteristics (such as author names, tests reported, type of physician examiner, herniation type and level) were presented in an easy-to-read table.

An in-depth description of the problems encountered with each study was provided. This helps explain why the neurologic testing to detect lumbar disc herniation and spinal nerve root involvement is not reliable enough to become a standardised test. Here’s a quick summary:

Most of the patients included in the studies had chronic pain with both sensory and motor function disturbances. This makes it more difficult to identify one test that would satisfy all diagnostic criteria.

Chronic pain patients often reduce their activity level and become deconditioned. This patient factor makes it difficult to tell clinically (without electrodiagnostic testing) when weakness is from nerve compression and when it is from deconditioning.

Sensory, motor and reflex testing was not always consistently performed and/or reported among the various studies published.

The decision to perform surgery was not clear in many cases. A clear, consensus- or evidence-based protocol for determining when surgery was needed does not exist.

Half of the studies did not describe testing procedures. For those studies that did describe the tests done, the way in which the tests were performed was not standardised – not the same from one study to the next.

It is known that the pathology and mechanism of disc herniation can be very complex. People have different responses and symptoms from the same level and degree of herniation. Sometimes there are overlapping symptoms from more than one spinal level. Even when electrodiagnostic tests are done to confirm nerve involvement, severe disc herniation can be present with no signs of weakness or sensory changes.

Currently, there are no neurologic clinical tests that have been shown to conclusively diagnose disc herniation based on the presence of radiculopathy (symptoms from compression on a spinal nerve root). Future studies are needed to find and standardise clinical tests that are valid and reliable in accurately diagnosing nerve root irritation (radiculopathy) associated with disc herniation.